3.
Network Effects: Promises & Challenges Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com Can Have the following advantage… … however Scalability as there is no central resource to exhaust Has to overcome to challenge of self organization from a collection of unreliable peers with unreliable connections Aggregating resources can lead to excellent performance Has to overcome the choking of the network of overhead or organizing messages Fault resilience as there is no single point of failure Has to overcome reliability challenges on account of network congestion, isolated networks, unreachable nodes

5.
Locating Content in P2P networks Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com Centralized Directory Approach Flooded Request Approach Document routing Approach Peers connect to a central directory where they publish information about the content that they have to share When the directory receives a request it replies with a peer in the directory that matches the request Criteria such as proximity, bandwidth, capacity, congestion, health, frequency can guide the decision Peers broadcast a request to its directly connected peers, each of whom broadcast to their directly connected peers and so on thru the network. This continues until the request is answered or some broadcast limit is reached. Each peer has helpful but only partially complete referral information. Each referral moves the requester closer to a peer that can satisfy the query. The network can scale with a number of central servers Generates a lot of ineffective network traffic which prevents scaling Can scale effectively as systems can complete a search within a bounded number of steps

17.
Gnutella Network Traffic A B D E C Each peer broadcasts requests to its connected peers and so on. The Pong descriptors may only be sent along the same path that carried the incoming Ping descriptor .mp3 .mp3 Get .mp3 Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

Creates a checksum for each piece (using the SHA1 hashing algorithm) and records it in the torrent file.

Peers that provide a complete file are called seeders

For sharing files:

Users download and open a torrent of interest with a BitTorrent client.

The client connects to the tracker(s) specified in the torrent file and receives a list of peers currently transferring pieces of the file(s)

The client connects to those peers to obtain the various pieces. Such a group of peers connected to each other to share a torrent is called a swarm .

For efficiency:

Download speed is controlled by Torrent tracking servers, who monitor all swarm users. I

Swarm users who share are rewarded by increasing the alotted swarm bandwidth

Those who leech and limit sharing, tracking servers are choked

To help newcomers, where the client reserves a portion of its available bandwidth for sending pieces to random peers Check sums ensure non corruption

Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

23.
BitTorrent: How it differs from HTTP Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com BitTorrent HTTP Makes many small data requests over different TCP sockets Typically a single HTTP GET request over a single TCP socket. Downloads in a random or in a &quot;rarest-first&quot; approach Downloads in a sequential manner. Downloads can take time to rise to full speed because it may take time for enough peer connections to be established, and it takes time for a node to receive sufficient data to become an effective uploader Rises to full speed very quickly and maintains this speed throughout.